The present invention relates to centrifuge apparatus.
Although it has been some time since the introduction of counter current chromatography instruments, these still remain in their infancy. One of the major factors restricting the use of counter current chromatography as an analytical tool is the speed at which a separation may be conducted. Another problem in the development of such instruments has been the inability to interface directly to a mass spectrometer detector without using a splitter.
For example, a prior art instrument with a coil of 350 ml capacity and internal diameter of 1.6 mm, is typically operated at a fluid flow of 2 ml per minute. With this structure, the separation time is approximately 3 hours. This does not provide a sufficiently fast separation for such an instrument to be of significant commercial use.
It is desirable to reduce both coil capacity (so that less sample material is required) and to reduce separation time. Capacity can be reduced by reducing the internal diameter of the coil. For example, there have been attempts to provide 90 ml capacity coils with internal diameter of 0.8 mm while retaining the same linear fluid flow by having a fluid flow rate of 0.5 ml per minute. Separation time can be reduced by reducing the length of the coil but so doing has led to the loss of resolution. For example, reducing the coil length by a factor of four to reduce capacity to 22.5 ml and separation time down to 45 minutes has only been achievable with a halving of resolution, which is not acceptable.
In addition, centrifuges for counter current chromatography typically have one or more coils of tubing of substantial length (many metres) wound onto one or more bobbins. The bobbins are rotated at high speeds, typically over 1,000 rpm. The sample to be separated is passed through the tubing during centrifuging, that is during rotation of the coils, which rotation causes the separation. A detector, typically UV but preferably a mass spectrometer, is provided to analyse the outlet fluid stream.
The conventional coil structures present several difficulties in the design and operation of such centrifuges. For example, the tubing tends to move and to unwind during operation of the machine. Although fixing mechanisms such as channels for holding each winding of tubing individually and the use of potting compounds to hold the coils have been used, these do not always prevent the problems and also add complexity and in some cases weight to the machine. Furthermore, the design of the coil winding tends to be limited to a simple helix arrangement.